Portsmouth
United Kingdom
Long-term weather forecast
Long-term weather forecast

September weather forecast and climate
Portsmouth, United Kingdom

September, the first month of the autumn, in Portsmouth, is still a comfortable month, with average temperature varying between 12.2°C (54°F) and 19°C (66.2°F).

Temperature

In Portsmouth, the average high-temperature is relatively the same as in August - a comfortable 19°C (66.2°F). In Portsmouth, United Kingdom, the average low-temperature is 12.2°C (54°F).

Rainfall

In Portsmouth, during 8.5 rainfall days, 53.7mm (2.1") of precipitation is typically accumulated. Throughout the year, there are 103.4 rainfall days, and 699mm (27.5") of precipitation is accumulated.

Sea temperature

September is the month with the warmest seawater, with an average sea temperature of 17.3°C (63.1°F).
Note: Swimming in 17.3°C (63.1°F) is not enjoyable for the majority. Controlling breathing becomes progressively more difficult as surface water temperature decreases below 21°C (69.8°F).

Daylight

The average length of the day in September is 12.6h.

Sunshine

The average sunshine in Portsmouth is 5.8h.

UV index

The average daily maximum UV index in September is 4. A UV Index of 3 to 5 symbolizes a medium health hazard from unsafe exposure to the UV radiation for the ordinary person.
Note: The daily maximum UV index of 4 in September interpret into the following advice:
Take precautions - Protection against the skin and eye damage is obliged. The Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes.

What is the temperature in September in Portsmouth?

The average high-temperature, in September, in Portsmouth, United Kingdom, is 19°C (66.2°F), while the average low-temperature is 12.2°C (54°F).

How many days does it rain in September in Portsmouth?

In Portsmouth, United Kingdom, during September, the rain falls for 8.5 days and regularly aggregates up to 53.7mm (2.1") of precipitation.

What is the month with the warmest sea water in Portsmouth?

September is the month with the warmest seawater in Portsmouth, with an average sea temperature of 17.3°C (63.1°F).

What is the sea water temperature in September in Portsmouth?

In Portsmouth, United Kingdom, in September, the average water temperature is 17.3°C (63.1°F). For swimming, a surface water temperature of 17.3°C (63.1°F) is not enjoyable for the majority. It is not considered safe, as controlling breathing becomes progressively more difficult as water temperature decreases below 21°C (69.8°F).

What is the average length of the day in September in Portsmouth?

The average length of the day in September in Portsmouth is 12.6h.

How long on average sun shines in September in Portsmouth?

The average sunshine in September in Portsmouth, United Kingdom, is 5.8h.

What is the UV index intensity in September in Portsmouth?

In Portsmouth, the average daily maximum UV index in September is 4. A UV Index value of 3 to 5 symbolizes a medium health risk from unprotected exposure to the UV radiation.
Average temperature in September - Portsmouth, United Kingdom
  • Average high temperature in September: 19°C

Warmest months (with the highest average high temperature) are July and August (21.4°C).
Months with the lowest average high temperature are January and February (8.2°C).

  • Average low temperature in September: 12.2°C

The month with the highest average low temperature is August (14.3°C).
The coldest month (with the lowest average low temperature) is February (2.8°C).

Average rainfall in September - Portsmouth, United Kingdom
  • Average rainfall in September: 53.7mm

The wettest month (with the highest rainfall) is October (86.2mm).
The driest month (with the lowest rainfall) is June (42mm).

Average rainfall days in September - Portsmouth, United Kingdom
  • Average rainfall days in September: 8.5 days

Months with the highest number of rainy days are January and December (11.2 days).
The month with the lowest number of rainy days is July (5.4 days).

Average sea temperature in September - Portsmouth, United Kingdom
  • Average sea temperature in September: 17.3°C

The best month for swimming (with the highest average sea temperature) is September (17.3°C).
The coldest month (with the lowest average sea temperature) is March (8.6°C).

Average daylight in September / Average sunshine in September - Portsmouth, United Kingdom
  • Average daylight in September: 12.6h

The month with the longest days is June (Average daylight: 16.4h).
The month with shortest days is December (Average daylight: 8h).

  • Average sunshine in September: 5.8h

The month with most sunshine is July (Average sunshine: 8.4h).
The month with least sunshine is December (Average sunshine: 2h).

Average UV index in September - Portsmouth, United Kingdom
  • Average UV index in September: 4

Months with the highest UV index are May, June, July and August (UV index 6).
Months with the lowest UV index are January, February, November and December (UV index 1).